Iron-sulfur protein FIGURE 15.6


Forms of carbon-bonded sulfur.



Organic forms of S represent up to 90% of the total soil S. These forms can be classified into two major types. C-bonded S constitutes up to 30% of the organic S and occurs in amino acids such as cysteine, cystine, and methionine; Fe-S proteins called ferrodoxodins; polypeptides; heterocyclic compounds such as biotin and thiamine, sulfinates, sulfones, sulfonates, and sulfoxides (Fig. 15.6). Sulfate esters are the second group and constitute 30-75% of the organic S in soil. These include sulfate esters (C-O-S), sulfamates (C-N-S), and sulfated thioglycosides (N-O-S) (Fig. 15.7). The measurement of this form involves reduction with hydroioidic acid (HI); thus it is often referred to as Hi-reducible S. This is considered to be the more biologically active or labile form in soil.

Soil microbial biomass S represents 2-3% of the total organic soil S. Microbial S is measured by lysing the cells with chloroform and measuring the S released to a CaCl2 or NaHCO3 extractant (Saggar et al, 1981). Arthrobacter and Pseudomonas contain roughly 10% of their S in an oxidized form regardless of whether they are grown at low or high levels of S substrate (Table 15.7). Fungi such as Fusarium and Trichoderma show a similar percentage when grown at low substrate S levels;

Choline sulfate -O3SO.

Was this article helpful?

0 0
Worm Farming

Worm Farming

Do You Want To Learn More About Green Living That Can Save You Money? Discover How To Create A Worm Farm From Scratch! Recycling has caught on with a more people as the years go by. Well, now theres another way to recycle that may seem unconventional at first, but it can save you money down the road.

Get My Free Ebook

Post a comment